Hi!
It's simple, but you have to know how.
You want to create .ewf-files. First let me get it clear: file1 from
195-200secs, and file2 195-300secs.
OK: Use your favourite editor to create
the_first.ewf:
source = file1.wav
offset = 195.0

the_second.ewf:
source = file2.wav
offset = 195.0

ecasound -a:1 -i the_first.ewf -ea:50 -a:2 -i the_second.ewf -ea:70
-a:all -o jack_alsa -z:mixmode,sum -c
NOTE: -c enables interactive mode, -z:mixmode,sum says that overall
amplitude will be at 100%, -ea:50 -ea:70, amplify sound to 50% and 70%, Ok
that adds up to 120, but I assumed one of the files may rather quiet at the
end. Output result to jack_alsa, you can use anything you like (OSS, alsa,
another file...)
Tipp: If you defintely want to limit processing time (overall length of the
output) to a time shorter than 105 (file2 plays from 195-300), then use the
option: -t:time_in_seconds (decimal values allowed).
HTH!
Kindest regards
Julien